In 1925 British adventurer Colonel Percy Fawcett disappeared into the wilds of the Amazon, never to be heard from again after going there in search of a lost city he called Z. But decades later, a city of sorts—actually a series of settlements connected by roads—has been found at the headwaters of the Xingu River where Fawcett went missing in an area previously buried beneath the dense foliage in what is now Xingu National Park.

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Anthropologist Michael Heckenberger of the University of Florida teamed with the local Kuikuro people in the Brazilian state of Mato Grosso to uncover 28 towns, villages and hamlets that may have supported as many as 50,000 people within roughly 7,700 square miles (20,000 square kilometers) of forest—an area slightly smaller than New Jersey. The larger towns boasted defensive ditches 10 feet (three meters) deep and 33 feet (10 meters) wide backed by a wooden palisade as well as large plazas, some reaching 490 feet (150 meters) across.

The remains of houses and ceramic cooking utensils show that humans occupied these cities for around 1,000 years, from roughly 1,500 years to as recently as 400 years ago. Satellite pictures reveal that during that time, the inhabitants carved roads through the jungle; all plaza villages had a major road that ran northeast to southwest along the summer solstice axis and linked to other settlements as much as three miles (five kilometers) away. There were bridges on some of the roads and others had canoe canals running alongside them.

The remains of the settlements also hint at surrounding large fields of manioc, or cassava (a starchy root that is still a staple part of the Brazilian diet) as well as the earthen dams and artificial ponds of fish farming, still practiced by people who may be the present-day descendants of the Kuikuro. Although such "garden cities," as Heckenberger describes them in Science, do not match the dense urbanism of contemporary Brazilian metropolises such as Rio de Janeiro or São Paulo, they do blend seamlessly into the jungle and maximize use of limited natural resources. They also suggest that the rainforest bears the marks of intense human habitation, rather than being pristine.

But, ultimately, these cities died; most likely a victim of the diseases brought by European explorers in the early 16th century, according to Heckenberger. Two thirds or more of the original human inhabitants of Brazil are believed to have been killed by such disease, and the forest quickly swallowed the cities they left behind.

As a result, later European explorers had no idea that a civilization had once flourished in the Amazon, despite clues in kilometer-long earthworks and unusually fertile so-called terra preta (dark) soil. The 500 or so Kuikuro may have known of their ancestors' exploits—and they may have drawn the attention of Fawcett and other explorers—but only now can the "lost cities" of the Amazon claim to have been found.